Automatic commutator for radiotelegraphic plants with indirect excitation.



E. GIRARDEAU.

AUTOMATIC GOMMUTATOR FOR RADIOTELEGRAPHIG PLANTS WITH INDIRECTEXGITATION.

- APPLICATION FILED DEC. 4, 1911.

1,105,029, Patented July 28, 1914.

Wicnesses Invenlol" I L44fwJ-M nnrrn 1 s'ra'rns a EMILE GIR ARBE'hU, OFPARIS, FRANCE, ASSIGNOR OF ONE-HALF T0 JOSEPH BETHENOD, 0F PARIS,FRANCE.

meantime coMMu'rAroR r01 o rq imonnnnenarmo PLANTS WITH mmnnc'rnxcr'rarron.

Specification of Letters Batent. Patented July 28, 1914.

flpplication nee December 4, 1911. Serial no. 683,772.

ToaZZ-wizom it may concern:

Be it known that l, Ema Grnl-xnnnlru, citizen of the French Republic,residing at Paris Republic of France, have invented certain new anduseful Improvements in Antomatic' Commutator's for RadiotelegraphicPlants with Indirect Excitation, of which the following is a s3e'cifi-cati0n.

This invention relates to radiotele'graphic plants with indirectexcitation.

The invention has for its object a device which automatically makes theplant ready as a receiver as soon as the lever of thekey is released.Thus a great rapidity i's realized with regard to the exchange of thetelegrams, the rapidity being almost the same as with ordinary Morsetelegraph's.

Owing to this invention the operators can interrupt the connection incase the receiver does notwork properly, or if there is any error in thetransmission or for any other reason.

In the accompanying drawings the invention is shown applied to a plantwith indi:

rect excitation by direct coupling.

A isthe antenna and P is the oscillatory sender circuit.

close as possible to the earth contact, an interrupter, the contacts 1and 2 of which are maintained separate by means of a spring 3 actingupon the movable contact 1. At the terminals of this interrupter, whichhas a very limited course only, (less than one millimeter), the primarycircuit of the receiver jigger J is branched oit, the receiver being ofany of the well known types. The contact between the contacts 1 and 2 isproduced by the excitation of the solenoid or electromagnet E suppliedwith current from a suitable source B through the intermediary of arheostat R. Under these conditions, when E, is at rest, there existsbetween the contacts 1 and 2 a small interval which is sutlicient tostop the direct passage of the waves collected by the antennae, saidelectric waves being thus forced to pass through the primary winding ofthe jigger and consequently to actuate the detector D. It however thetransmitting key M adapted for example to act (by means of a device notrepresented as not essential) upon the current of the source, isdepressed, it closes an auxil- According to this inventionthere isinserted at: G, at a point which is as 'iary contact (not represented)which makes the electrom'agnet E ready to operate; and the contacts 1and 2 conic at once in contact witheach other, the primary Winding ofthe jigger J being short-circuited, 'which generally, in a plant ofmedium size, is suffici'ent to insure the protection of the receiverdevices. It has already been proposed to use for the last auxiliarycontact a spring or equivalent device, in order to permit further theclosing of the sender contact by means of the same key M. The adjustmentof these two contacts must therefore be made with a great precision andobliges to use very complicated keys. According to the presentinvention, in order to avoid this great difiiculty, the s0lenoid"orelectromagnet E is supplied by a suitable source' B through theintermediary of a rheo stat R, and when the key M is at rest, itsrocker, being in contact with the stop bar 5', short-circuits thewinding of E,,- which is thus rendered inoperative. The closing of theinterrupter C is affected when the electromagnet E, ceases to beshort-circuited, namely a's soon as the contact 4, 5 is opened. -Thislast cont-act does not necessitate any spring, as 5" is the stop bar ofthe key, and the operation is certainly good, whatever the course of thekey M may be, which is no more complicated than an ordinary Morse key.The rheostat R serves to prevent the short circuiting of the source Bofenergy when .the key is at rest and it further reduces thetime-constant of the circuit B, R, E, and thus improves the workingconditions.

With very powerful plants, such as shown in the drawings, the safetydevice hereinbefore described can be completed by disposing in thesecondary jigger circuit a commutator l, the rocker'6 of which is pushedagainst the terminal 8 through the action of the spring 9 so that thesaid commutator I closes the secondary circuit comprising the detectorD, the apparatus being thus ready for reception. As soon however as therocker 4 of the key M goes away from the stop bar 5, a solenoid Econnected in series with E pulls the rocker 6 away from the terminal 8and brings the same in contact with the terminal 7. Under theseconditions there is not only the secondary circuit interru ted duringemission but the secondary win ing of the jigger J is short-circuitedupon itself, the detector D being thus protected in the verybest manner.

One of the advantages of the installation shown in the drawings is thatowing to the very short course of the interrupter C and of thecommutator I, the electrodes 1 and 2 on the one hand and 7 and 8 on theotherhand serve in any case as lightning-arresters for limiting thetension, protecting thus the receiver apparatus in case the circuit B, E

E R should accidentally not work properly.-

, and with a second circuit one of the ends sending o of which isbranched ofl between the electromagnet and the battery, its second endbeing branched off between the electro-magnet and the resistance, thissecond circuit comprising an interrufpter the movable part of whichconsists o the sender and opens the said second circuit if the saidsender is being depressed. v

2. In a receiver for wireless telegraphy an electro manet automaticallyexcited by the a signal, a commutator whose spring influenced arm isattracted by the e ectro-magnet at the moment when asignal is sent, afirst circuit of which one end is electrically connected with the arm ofthe commutator, said circuit comprising the secondary winding of thejigger and a conductor without lumped self induction or capacity whichis connected with the contact of the commutator on which the arm of .thecommutator is pressed when the electromagnet is excited, said contactforming thus the second end of said first circuit; a second circuit oneend of which is placed between the secondary winding of the jigger andthe said conductor and the other end of which is on the contact againstwhich bears the arm of the commutator through the action of the springwhen the electro-magnet is not excited, this second circuit comprisingthe detector and a condenser.

3. In an apparatus for wireless telegraphy the combination of asenderwith a circuit comprising a pile or battery, a resistance, aprotectmg commutator of the receiving circuit, a first electro-magnetwhich, when it is excited operates the protecting commutator of thereceiving circuit, and a second electro-magnet the armature of which,when excited, grounds the antenna, and with a second circuit one end ofwhich is branched between the'electro-magnets and the battery, itssecond end being branched off between the electro-magnets and theresistance, this second circuit comprising an interrupter the movablepart of which consists of the sender and opens the .saidsecond circuitwhen said sender is being depressed.

In witness whereof I have hereunto set my hand in the presence of twowitnesses EMILE GIRARDEAU.

Witnesses i H. C. CoxE, ALBERT DE CARSALADE.

